5. Standard conditions. Standard conditions

We have shown that a two-phase pure body has a variance equal to 1. This means that the equilibrium temperature between phases can only be defined unambiguously if we fix the value of the pressure.

• The temperature scale was constructed from measurements of two-phase water equilibria defined under a particular pressure, normal atmospheric pressure p ₀ .

  Normal pressure is equal to p ₀ = 101,325 Pa (= 1 atmosphere).

  Thus, t = 0 °C corresponds to the liquid-solid equilibrium of pure water under pressure p ₀ and t = 100 °C is the temperature for which the saturating vapor pressure of pure liquid water is p _...